Briefly:
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High-permeability alloys such as mumetal and Alloy 49 are the standard materials for blocking low-frequency magnetic interference in electronics, medical devices, and aerospace systems.
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New England is home to experienced fabricators who supply these materials in stock form and as custom-engineered shields.
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Selecting the right material depends on field frequency, flux density, and the geometry of the application.
Engineers and procurement teams seeking Magnetic Shielding Materials in New England, ND will find a mature supply base capable of providing both raw stock and fully fabricated custom shields. The region’s manufacturing heritage supports specialized metallurgical work that most general sheet-metal shops cannot replicate.
Understanding High-Permeability Shielding Alloys
In operation, a magnetic shield absorbs magnetic flux by providing a path around a sensitive area and protecting the electronics found within a particular magnetic shield. The effectiveness of that path depends almost entirely on the material’s magnetic permeability.
The shielding capability of these materials arises from their high magnetic permeability, which provides a low-reluctance path for magnetic flux that steers magnetic field lines around the shielded volume. Two alloy families dominate practical applications:
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Mumetal (ASTM A753 Alloy Type 4): A soft magnetic nickel-iron alloy with about 80% nickel, 4.2-5.2% molybdenum, a saturation induction of approximately 8,000 Gauss, the highest technically obtainable permeability (Max greater than 350,000), and a very low coercive force.
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Alloy 49 (medium permeability): Some magnetic shielding applications may call for high permeability mumetal, while another may call for medium permeability Alloy 49. Frequently, there is a need for a combination of both mumetal and Alloy 49 magnetic shields.
Frequency is an important factor of magnetic fields. The frequency range of the magnetic field that needs to be shielded should be considered when selecting the appropriate shielding material, as the material will respond differently to the different frequencies.
According to the IEEE EMC Society’s shielding characterization guidance, absorber design depends on the frequency range, the quantity of shielding required, and the physical characteristics of the devices being shielded.
Material Forms Available and How to Choose
If you plan to manufacture your own magnetic shields using mumetal or Alloy 49, these magnetic shielding materials are available in sheets, foils, round bar, wire, plates, forgings, and seamless tubing. Not just a fabricator of custom magnetic shields, a qualified supplier is also a distributor of magnetic shielding materials.
All magnetic shielding materials should meet ASTM A753 Alloy Type 2, 3, or 4 and be sourced from only the finest domestic and international mills.
The table below summarizes the most common stock forms and their typical use cases:
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Material Form |
Typical Use Case |
Key Advantage |
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Sheet / Coil |
Box enclosures, flat panels |
Easy to cut, stamp, and bend |
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Seamless Tubing |
Cylindrical shields, sensor housings |
Tighter tolerances, no weld seam |
|
Foil |
Thin-layer wrapping, small components |
Lightweight, flexible application |
|
Round Bar / Plate |
Machined parts, heavy-duty enclosures |
High material volume for complex geometries |
In lower flux density fields, high permeability materials provide greater attenuation. In higher field densities, mumetal becomes saturated and loses its effectiveness. In these cases, steel provides good attenuation and a much higher saturation threshold. Understanding this trade-off before ordering stock prevents costly redesigns.
Industry leaders in high-precision sheet metal fabrication and bar stock machining of high permeability mumetal and HyMu 80 maintain vacuum and hydrogen furnaces on-site used for both in-process stress relief annealing and final heat treatment. The final heat treatment ensures maximum magnetic permeability on all magnetic shields.
Industries Served and Practical Applications
For over 60 years, fabricators of custom magnetic shielding have served the Medical, Defense, Aerospace, Biochemical, and Aviation industries. The range of applications is broad:
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Medical imaging: Sensitive MRI and MEG equipment requires low-noise environments where stray fields are tightly controlled.
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Aerospace and defense: MuShield is the industry’s sought-after choice for consulting, building, and delivering magnetic shields utilized in the aerospace market from the earth’s soil to the starlit atmosphere.
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Electronics manufacturing: The shielding material, generically referred to as mumetal, absorbs the electromagnetic interference being emitted, or serves as a shield for sensitive devices from ambient magnetic interference.
Engineering staff at a qualified fabricator will work with the client, solving the magnetic shielding problem through FEA modeling, experimentation, and prototyping. From design concept to customer review through manufacturing, great attention to detail is made, ensuring the highest quality product.
Frequently Asked Questions
What is the difference between mumetal and Alloy 49 for shielding? Mumetal offers the highest available permeability, making it the preferred choice when a permeability value above 250,000 is required. Some magnetic shielding applications may call for high permeability mumetal, while another may call for medium permeability Alloy 49. Alloy 49 is often selected when moderate permeability is sufficient and cost reduction is a priority.
Does the shape of the shield affect performance? Yes. When cylinders will not fit in an application and a box-shaped magnetic shield is more practical for mechanical or structural reasons, fabricated sheet metal boxes are the next best choice. Bend radii should be as large as possible because the magnetic flux permeating through the shielding material does not turn on sharp edges easily and flux leakage can occur. The least favorable magnetic shielding shape is a large flat sheet.
Is heat treatment always required after fabrication? After diving into specific magnetic shielding needs, more often than not, fabricators end up quoting to fabricate a magnetic shield complete with hydrogen heat treatment for maximum magnetic permeability. Heat treatment restores permeability lost during cold-working operations such as bending, stamping, and welding.
Can raw material stock be ordered without custom fabrication? Stocking magnetic shielding materials saves customers time and money, as suppliers are able to ship raw material within a day or two of an order being placed. Sample kits are also available for initial design testing before committing to a full production run.
Work With an Established New England Supplier
For organizations sourcing magnetic shielding materials in New England, partnering with a supplier that holds engineering expertise alongside material inventory eliminates the gap between raw stock and a finished, tested shield. For over sixty years, The MuShield Company has been a worldwide industry leader in manufacturing custom magnetic shields, precision sheet metal fabrication, and Hydroforming solutions. The company is fully AS9100D certified and ITAR registered, supporting defense and aerospace procurement requirements.
Contact The MuShield Company to discuss material specifications, request a sample kit, or submit a design for engineering review.
